One of the reason I put picture on Flickr is 'Geo tagging'. Basically you've add another metadata about geographic information where you've took the shot. You've not have to have GPS receiver to do this but as long you know the location quite well you can add it directly. Oh you can link the camera with GPS and store it with other digital information (date, time, ISO, exposure etc) but only D200 and another D's pro series (D2X, D2Xs, D2H, D2Hs) able to do it.
For this purpose I carried along GPS receiver to actively track me during the trekking. Start from Lukla (2840m) until Gorak Shep (5125m) I also put waypoints to determine the places I thought the most important. On my hand is a very good map from National Geographic which is show contour and elevation. GPS did the job to record the tracking and my duration of walk. For direction I relayed on the intuition and common senses. The path quite easy anyway, you will not getting lost there.
So if you see my pictures on Flickr go to the Nepal : an ordinary women journey set. Then you will see on top click "Map" under the title. From there the page turn to Yahoo Map and the pink dot showed the number and location of my pictures. Note : choose 'satellite' rather than 'map' on the right bar.
To put the location about right I'm using data I collected from GPS to compare the map. I transfer GPS data into Google Earth (GE) then it will produced the path of the trek I've done. GE is lots better in term of pixel resolution compare with Yahoo Map. And also has similar photo tagging with Panoramio. As you might see GE has very high resolution map on top of Khumbu glacier and Everest. I even can see walk path from here.
Adding geographic information on photos basically to help people imagine the place I went. But for me mainly to help build memory back of what I have done. Gosh ! why I am so forgetful....